Emit particles as a cone shaped beam
(Blend file below)

The emitter is just a section of a standard UV sphere.
Particles are launched evenly from it's faces so the pattern is radial.

The emitter is placed inside 2 solidified but invisible cones that are setup as &quot;collision objects&quot; (physics) so they effectively focus/deflect particles.

If any escape in your version, try increasing the &quot;Particles --&gt; Physics --&gt; Subframe&quot; slider, but be mindful that each increment will labour your computer further.
In this example, (Blender Vers 2.77) the default particle settings were used throughout, apart from the emitter and draw size. (in Display tab)
With this arrangement, force fields or other coersions aren't necessary.  The number and size of the particles plus the renderer used will determine how dense it looks.
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The circular 'Nav-handle' is a common parent that holds it all together for when the emitter is to be animated,